456 SOME RESULTS OF THE INTERNATIONAL FISHERY INVESTIGATIONS. 



to be of advantage for the direction of the continental eel fisheries, the 

 importance of this discovery can hardly be over-estimated. We now 

 know that the lack of success which has attended the innumerable 

 attempts to find Leptocephali in shallow in-shore waters, and even in 

 restricted sea areas, like the Baltic, the Cattegat, the North Sea, or the 

 Irish Sea, is due to the fact that these larvse do not frequent those 

 waters, and that the rare captures which are recorded in the literature 

 are those of individuals the development of which has for some reason 

 or other been greatly retarded. There is no longer any doubt that the 

 eel does not spawn in fresh water, but must emigrate to the open sea 

 before it can reproduce. If it is hindered from making this migra- 

 tion it will die without spawning. Further, the fish spawns in deep 

 and relatively warm water in the open Atlantic, north-west and west 

 from Scotland. To reach this region the parents must pass through the 

 Baltic if they have been living in some of the great continental rivers, 

 and most of the North European fresh-water eels must make a very 

 lengthy spawning migration, in the course of which they traverse the 

 North Sea, the Irish Channel, or the English Channel before they 

 attain the conditions necessary for the maturation of the reproductive 

 organs. It will readily be seen that a complete knowledge of these 

 migration paths and seasons, such as no doubt will soon be obtained by 

 following up these observations, must prove of great importance, not 

 only for the development of more rational methods of fishing, but also 

 for the elaboration of useful legislation regulating the fishery. 



Following up Schmidt's discovery of Leptocephali in the Atlantic, 

 Johausen has materially added to our knowledge of the life history of 

 the eel in its " elver " stages. It is well known that the elvers, which 

 are the metamorpliosed Leptocephali, ascend the rivers from the sea 

 in immense numbers in the spring of the year. But our knowledge 

 of the elvers in the sea itself has hitherto been very scanty. Again 

 the explanation is that they were not looked for in the proper time and 

 manner. The young metamorphosed eels are pelagic at night, that is, 

 they swim at some distance from the bottom in intermediate depths. 

 During the day, on the other hand, they live on the sea bottom. In 

 the sea the elvers are almost colourless, though they differ greatly from 

 the leptocephaline stages. A smoky-brown pigment first appears on 

 the tip of the tail and on the head. As the transformation from the 

 Leptocephalus to the elver stages proceeds this pigment gradually 

 invades the rest of the body. At the same time the peculiar ribbon- 

 like form of the Leptocephalus is lost ; the little fish becomes thicker 

 from side to side and less deep from back to belly. Curiously enough, 

 too, it becomes actually shorter from head to tail. The almost colour- 

 * Mcdd. Komm. JIavtmdersog., Fiskeri, Bd. i. Nr. 6, 1905. 



